This application relates to tower grain dryers, and, in particular to a tower dryer in which the function of plenum adjustment ratio and divider/hopper is combined in a single unit.
A grain tower dryer typically comprises a central plenum defined by a porous (or air pervious) wall. The tower also includes an outer porous (or air pervious) wall spaced from the plenum wall. The plenum wall and outer wall define an annular column through which grain to be dried fall. A heater/blower is typically positioned within the plenum. The heater/blower draws cool air in through a bottom portion of the grain column and expels heated air out through an upper portion of the grain column. Hence, the grain falls through an upper heating section (where the grain is dried) into a lower cooler section (where the grain is cooled).
On occasion, it is desirable to change the ratio of the length of the heating section to the length of the cooling section. Hence, plenum dividers have been devised. One example of a plenum divider is shown in U.S. Pat. No. 4,249,891. As set forth in this patent, the plenum divider comprises two or more pivotal doors which are placed in the plenum and each of which rotates between a horizontal closed position and an open position. When one door is in the horizontal closed position, all doors above the closed door are opened. The closed door defines a floor for the heating section, and thus separates the heating section from the cooling section. By selecting which doors are opened and closed, the ratio of the length of the heating section to the length of the cooling section can be altered.
As the grain falls through the grain column, particulate matter can pass through the plenum wall to drop down through the plenum (as opposed to the grain column). Divider/hoppers have been installed in some grain drying towers without plenum dividers. Examples of such a divider/hopper is shown in U.S. Pat. No. 3,896,562. Similar divider/hoppers are included in some of the F-Series Farm Fan Tower Dryers available from ffi, inc. and in some of the T-Series tower dryers available from The GSI Group. However, to our knowledge, such hoppers have not been installed in dryers with plenum dividers. As can be appreciated, the use of the standard doors, such as disclosed in the above noted patents, will simply provide different flat surfaces on which the particulate matter can collect. Thus, we are not aware of any tower dryer that includes both a divider/hopper and a plenum wherein the ratio of the length of the heating portion of the plenum to the length of the cooling portion of the plenum can be adjusted.